Approximately two million cataract surgery procedures are performed in the United States annually. The procedure generally involves making an incision in the anterior lens capsule to remove the cataractous crystalline lens and implanting an intraocular lens in its place. The power of the implanted lens is selected (based upon pre-operative measurements of ocular length and corneal curvature) to enable the patient to see without additional corrective measures (e.g., glasses or contact lenses). Unfortunately, due to errors in measurement, and/or variable lens positioning and wound healing, about half of all patients undergoing this procedure will not enjoy optimal vision without correction after surgery. Brandser et al., Acta Ophthalmol Scan 75:162-165 (1997); Oshika et al., J. Cataract Refract Surg 24:509-514 (1998). Because the power of prior art intraocular lenses generally cannot be adjusted once they have been implanted, the patient typically must choose between replacing the implanted lens with another lens of a different power or be resigned to the use of additional corrective lenses such as glasses or contact lenses. Since the benefits typically do not outweigh the risks of the former, it is almost never done.
An intraocular lens whose power may be adjusted after implantation and subsequent wound healing would be an ideal solution to post-operative refractive errors associated with cataract surgery. Moreover, such a lens would have wider applications and may be used to correct more typical conditions such as myopia, hyperopia, and astigmatism. Although surgical procedures such as LASIK which uses a laser to reshape the cornea are available, only low to moderate myopia and hyperopia may be readily treated. In contrast, an intraocular lens, which would function just like glasses or contact lenses to correct for the refractive error of the natural eye, could be implanted in the eye of any patient. Because the power of the implanted lens may be adjusted, post-operative refractive errors due to measurement irregularities and/or variable lens positioning and wound healing may be fine tuned in-situ. One solution has been proposed in U.S. Pat. No. 6,450,642. In this patent, optical elements such as intraocular lenses are created having a refraction modifying composition (RMC) dispersed throughout the lens. Dispersion of the RMC throughout the lens is accomplished by forming the base lens in the presence of the RMC. The result is a lens whose optical properties can be adjusted by localized polymerization of the RMC.
While this process is effective in creating an adaptable lens, the presence of the macromer during the formation process often results in at least some of the macromers being polymerized into the matrix of the lens. This reduces the amount of macromer available for subsequent polymerization. Additionally, the polymerization reaction of the base polymer must be mutually exclusive from the polymerization of the macromer.
It is desirable, therefore, to make a material whose properties can be manipulated through the use of modifiers dispersed in the material in a manner that the modifiers are not consumed during the initial fabrication process and the base material can be polymerized by any polymerization reaction including photo-polymerization.